(PECL gmagick >= Unknown)
GmagickPixel::getcolorvalue — Gets the normalized value of the provided color channel
$color): floatRetrieves the value of the color channel specified, as a floating-point number between 0 and 1.
colorThe channel to check, specified as one of the Gmagick channel constants.
The value of the channel, as a normalized floating-point number, throwing GmagickPixelException on error.